simple heater question .....

Minion · 13th March 2011, 05:37 PM

Hi guys , here is a stupidly easy question for you ......

I"m running 6.3v AC heaters and the data sheet for the 12ax7 says that at 6.3v the heater draws 300ma Current ...... is that 300ma (150ma per triode) per tube or 300ma per triode (600ma per tube) .......

I need to know becasue my 6.3v tap is putting out 7.75v under a load (2 x 12ax7) and I need to calculate what resistor to use to drop it to 6.3v ....

thanx

Eli Duttman · 05:55 PM

Each section of the 'X7 draws 150 mA. of heater current. Connect the sections' heaters in series and you need 12.6 VAC/150 mA. Connect the sections' heaters in parallel and you need 6.3 VAC/300 mA.

Minion · 13th March 2011, 05:58 PM

Thank you very much ...... I"m connecting two 12ax7 tubes in paralell , so 2 tubes or 4 sections will draw 600ma total ..... Thanx a lot

Poindexter · 14th March 2011, 03:28 AM

Well stated, Eli.

P

13th March 2011, 05:37 PM	#1
Minion diyAudio Member Join Date: May 2006	simple heater question ..... Hi guys , here is a stupidly easy question for you ...... I"m running 6.3v AC heaters and the data sheet for the 12ax7 says that at 6.3v the heater draws 300ma Current ...... is that 300ma (150ma per triode) per tube or 300ma per triode (600ma per tube) ....... I need to know becasue my 6.3v tap is putting out 7.75v under a load (2 x 12ax7) and I need to calculate what resistor to use to drop it to 6.3v .... thanx

13th March 2011, 05:54 PM	#2
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	Each section of the 'X7 draws 150 mA. of heater current. Connect the sections' heaters in series and you need 12.6 VAC/150 mA. Connect the sections' heaters in parallel and you need 6.3 VAC/300 mA. __________________ Eli D. Last edited by Eli Duttman; 13th March 2011 at 05:55 PM. Reason: fixed typo

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13th March 2011, 05:58 PM	#3
Minion diyAudio Member Join Date: May 2006	Thank you very much ...... I"m connecting two 12ax7 tubes in paralell , so 2 tubes or 4 sections will draw 600ma total ..... Thanx a lot

14th March 2011, 03:28 AM	#4
Poindexter diyAudio Member Join Date: Oct 2004 Location: Maui, Hawai'i, USA	Well stated, Eli. P

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